The present invention relates to a power feeding apparatus suitable for transferring power, a power receiving apparatus, a power transfer system, a power supply method, a portable apparatus, and a timepiece.
A small electronic timepiece, such as a wristwatch, may include therein a small primary battery, a clock circuit, and a clock-hand mechanism. In general, power supplied from the primary battery is employed to drive the clock circuit, the clock-hand mechanism, and the like. Such an electronic apparatus including the primary battery has a problem in that the battery must be replaced or discarded.
Accordingly, the electronic apparatus may include a rechargeable secondary battery. A feed terminal for charging the secondary battery may be provided on an outer casing of the electronic timepiece.
When the feed terminal is provided on the outer casing of the electronic apparatus, there is a problem in that the feed terminal may become corroded. In particular, the feed terminal used in the electronic timepiece to be wrapped around a wrist of a user with a belt is apt to be corroded by sweat from the user or by water, thus degrading charging reliability. In addition, the electronic apparatus with a structure having the exposed feed terminal is difficult to be made waterproof.
Internal circuits of the electronic apparatus may pick up noise from the feed terminal, thus causing malfunction of the electronic apparatus. For example, when a user having the electronic timepiece around the wrist uses a cellular phone, electromagnetic waves emitted from the cellular phone may enter the electronic timepiece through the feed terminal as noise and cause malfunction of the electronic timepiece. An electronic apparatus having a data input/output terminal for inputting/outputting data has a similar disadvantage in that it may pick up noise.
In order to solve the battery waste problem, it is possible to propose a system in which the electronic timepiece is externally irradiated with electromagnetic waves, internally receives the electromagnetic waves, and converts the received electromagnetic waves into electrical power. Since metal has a property of blocking the electromagnetic waves, it is impossible to use metal for a casing portion of the electronic apparatus in this system.
A battery charger for charging a cellular phone including the built-in secondary battery is larger than the cellular phone itself. In addition, the battery charger generates the voltage required to charge the secondary battery by receiving power from a commercial power supply. Thus, it is impossible to easily charge the cellular phone.
Accordingly, it is an object of the present invention to provide a power feeding apparatus for supplying power by means of vibrations and a power receiving apparatus for receiving power from the vibrations from the power feeding apparatus. It is another object of the present invention to transmit data using vibrations.
A power feeding apparatus according to the present invention converts electrical power into vibrations and thereby transfers the electrical power to a power receiving apparatus. The power feeding apparatus includes a vibration exciter including a contact surface to be in contact with the power receiving apparatus and an excitation surface to be vibrated; an actuator for vibrating the excitation surface of the vibration exciter; a power supply for feeding power; and a drive circuit for receiving power from the power supply and outputting a driving signal for driving the actuator.
According to the present invention, the power feeding apparatus converts electrical power into vibrations and thereby outputs the electrical power to the power receiving apparatus. Therefore, it is not necessary to provide a terminal electrode for supplying power to the power feeding apparatus. Hence, problems of potential corrosion and of noise being picked up from the terminal electrode cannot occur.
Preferably, the actuator includes a piezoelectric device. Since a piezoelectric device can be miniaturized, it is suitable for miniaturization of the apparatus. The actuator may vibrate the vibration exciter longitudinally, i.e., in a direction perpendicular to the contact surface. Alternatively, the actuator may cause the vibration exciter to vibrate torsionally.
The vibration exciter may be part of a casing of the power feeding apparatus. In this case, the vibration exciter can be formed at the same time as the casing is formed. Hence, the number of components of the power feeding apparatus can be reduced.
A power receiving apparatus according to the present invention includes a vibrator to be displaced by vibrations of the apparatus; a converter for converting displacements of the vibrator into electrical power; and a secondary battery for storing electrical power obtained by the converter. According to the present invention, it is not necessary to provide the power receiving apparatus with a terminal electrode for receiving power. Hence, problems of potential corrosion and of noise being picked up from the terminal electrode cannot occur. Since electrical power transferred to a secondary battery can be accumulated, it is possible to obtain electrical power from the secondary battery and to use the electrical power after the power transfer is terminated.
The converter may include a piezoelectric device, and the piezoelectric device may obtain voltage generated by the displacement of the piezoelectric device as the electrical power. The vibrator and the converter may be integrated, and the converter may obtain electrical power by resonance. In this case, the piezoelectric device is greatly displaced, so that a large electromotive voltage can be obtained.
The vibrator may be connected to a casing of the apparatus. Alternatively, the vibrator may be part of the casing of the apparatus. In this case, the vibrator can be formed at the same time as the casing is formed. Therefore, the number of components can be reduced.
A portable apparatus according to the present invention includes a power receiving apparatus and a power-using unit activated by power supplied from the secondary battery.
The portable apparatus may be stored in a storage case including a convex portion protruding from an inner wall. The portable apparatus may include a concave portion into which the convex portion is inserted. The concave portion may be formed in the vibrator. Alternatively, the portable apparatus may be stored in a storage case including a concave portion in an inner wall of a bottom surface. Preferably, a convex portion engageable with the concave portion is formed on a bottom surface of the apparatus and the vibrator is a casing of the apparatus. In this case, the portable apparatus is vibrated by vibrations from the movements of a user carrying the portable apparatus in the storage case. Hence, the concave portion as the vibrator or the casing itself is vibrated, thus charging the secondary battery.
A timepiece according to the present invention includes a power receiving apparatus and a clock unit for receiving power supplied from the secondary battery and for measuring time.
A power, transfer system according to the present invention includes a power feeding apparatus and a power receiving apparatus. Electrical power is transferred from the power feeding apparatus to the power receiving apparatus by transmitting vibrations of the vibration exciter to the vibrator.
In this case, it is preferable that the vibration exciter protrude from the power feeding apparatus and engage the power feeding apparatus. According to the present invention, the vibration exciter serves both as the vibration exciter and the holder.
Alternatively, one of the vibration exciter and the vibrator may be provided with a concave portion and the other with a convex portion, and the concave portion and the convex portion may be engageable with each other. In this case, the vibration exciter and the vibrator can be intimately connected. Hence, the vibrations can be efficiently transmitted, thus improving the power transmission efficiency.
Preferably, the drive circuit drives the actuator so that the vibration exciter vibrates at a frequency near a natural oscillation frequency of the vibrator and the converter as one united body. In this case, the vibrations can be transmitted by resonance. Hence, large amounts of electrical power can be obtained from the converter.
The vibration exciter may vibrate the vibrator intermittently and the vibrator may obtain electrical power in the course of vibration attenuation.
A power transfer method according to the present invention feeds electrical power from a power feeding apparatus including a power supply, an actuator, and a vibration exciter to a power receiving apparatus including a vibrator. The power transfer method includes the steps of receiving power from the power supply and driving the actuator; vibrating the vibration exciter by the actuator; vibrating the vibrator by the vibration exciter; and converting vibrations of the vibrator into electrical power. According to the present invention, electrical power can be transferred by means of vibrations.
A power transfer method according to the present invention transfers electrical power and data by means of vibrations between a power feeding apparatus including a first piezoelectric device and a first vibration transmission member connected to the first piezoelectric device and a power receiving apparatus including a second piezoelectric device and a second vibration transmission member connected to the second piezoelectric device. The power transfer method includes the step of bringing the first vibration transmission member into contact with the second vibration transmission member; and executing, using time-sharing, a first period for transferring electrical power from the power feeding apparatus to the power receiving apparatus, a second period for transmitting first data from the power feeding apparatus to the power receiving apparatus, and a third period for transmitting second data from the power receiving apparatus to the power feeding apparatus. According to the present invention, not only electrical power but also data can be transmitted in either direction.
In this case, the first period may include the steps of applying voltage to the first piezoelectric device and vibrating the first piezoelectric device; vibrating the first vibration transmission member by the first piezoelectric device; vibrating the second vibration transmission member by the first vibration transmission member; and obtaining electrical power based on an electromotive voltage of the second piezoelectric device. The second period may include the steps of applying voltage to the first piezoelectric device in accordance with the first data and vibrating the first piezoelectric device; vibrating the first vibration transmission member by the first piezoelectric device; vibrating the second vibration transmission member by the first vibration transmission member; vibrating the second piezoelectric device by the second vibration transmission member; and reading the first data based on the electromotive voltage of the second piezoelectric device. The third period may include the steps of applying voltage to the second piezoelectric device in accordance with the second data and vibrating the second electric voltage; vibrating the first vibration transmission member by the first piezoelectric device; vibrating the second vibration transmission member by the first vibration transmission member; vibrating the second piezoelectric device by the second vibration transmission member; and reading the second data based on the electromotive voltage of the second piezoelectric device.